An opening or gap is purposely provided between adjacent concrete structures for accommodating dimensional changes within the gap occurring as expansion and contraction due to temperature changes, shortening and creep of the concrete caused by prestressing, seismic cycling and vibration, deflections caused by live loads, and longitudinal forces caused by vehicular traffic. An expansion joint system is conventionally installed in the gap to provide a bridge across the gap and to accommodate the movements in the vicinity of the gap.
Bridge and roadway constructions are especially subject to relative movement in response to the occurrence of thermal changes, seismic events, and vehicle loads. This raises particular problems, because the movements occurring during such events are not predictable either with respect to the magnitude of the movements or with respect to the direction of the movements. In many instances bridges have become unusable for significant periods of time, due to the fact that traffic cannot travel across damaged expansion joints.
Modular expansion joint systems typically employ a plurality of spaced-apart, load bearing members or “centerbeams” extending transversely relative to the direction of vehicle traffic. The top surfaces of the load bearing members are engaged by the vehicle tires. Elastomeric seals extend between the load bearing members adjacent the tops of the load bearing members to fill the spaces between the load bearing members. These seals are flexible are therefore stretch and contract in response to movement of the load bearing members. A plurality of elongated support members are positioned below the transverse load bearing members spanning the expansion gap between the roadway sections. The support members extend longitudinally relative to the direction of the vehicle traffic. The elongated support members support the transverse load bearing members. The opposite ends of the support members are received in a housing embedded in the roadway sections.
In single support bar (SSB) modular expansion joint systems, a single support member is connected to all the transverse load bearing members. The load bearing member connection to the single support bar member commonly consists of a yoke. The yoked connection of the single support bar member to a plurality of transverse load bearing members provides a sliding or pivoting connection in the SSB modular expansion joint systems.
In a multiple support bar (MSB) modular expansion joint system, each transverse vehicular load bearing member (centerbeam) is rigidly connected to a single longitudinal support bar member. The use of yoked connections between the transverse vehicular load bearing members and the longitudinal support bar members has heretofore not been disclosed or indicated for MSB modular expansion joint systems, as MSB connections are rigid and have no need for sliding or pivoting capability.
In typical multiple support bar (MSB) expansion joint systems used in the industry, each longitudinal support bar member is welded to only one transverse vehicle load bearing member. Each transverse vehicle load bearing member is rigidly connected to its own support member by full penetration welds. While the full penetration weld connection does provide considerable structural strength and rigidity that is necessary in the rugged environment of an expansion joint, the welding poses a drawback as it is difficult to fabricate. The weld must be ultrasonically tested to pass the job specification and qualify for use. Failures of the full penetration welds used to connect a load bearing member to its own support member in MSB expansion joint systems require substantial and expensive efforts to repair the weld. In order to be adequately repaired, the weld must be severed, ground and rewelded at significant expense and time-delay.